In recent years, water-absorbent resins for absorbing body fluids (urine and blood) are widely used as one of constituent elements (a main constituent element) of a sanitary material (absorbing product) such as a paper diaper, a sanitary napkin, and an incontinence pad.
Known water-absorbent resins include, for example, partially neutralized and cross-linked polyacrylic acid, hydrolyzed starch-acrylonitrile graft polymer, neutralized starch-acrylic acid graft polymer, saponified vinyl acetate-acrylic ester copolymer, cross-linked carboxymethyl cellulose, hydrolyzed acrylonitrile copolymer or acrylamide copolymer, or cross-linked acrylonitrile copolymer or acrylamide copolymer, cross-linked cationic monomer, cross-linked isobutylene-maleic acid copolymer, and cross-linked copolymer of 2-acrylamido-2-methylpropane sulfonic acid and acrylic acid.
The water-absorbent resin has been conventionally desired to have the following absorbent characteristics: a high absorption capacity, a high absorption rate, liquid permeability, gel strength of swelling gel, an absorbent amount at which water is absorbed from a base material containing aqueous fluids, and the like, when the water-absorbent resin comes into contact with aqueous fluids such as body fluids.
Further, the water-absorbent resin used in a diaper, particularly in an adult diaper, is required to have not only the aforementioned absorbent characteristics but also a deodorant characteristic as an additional function.
Conventionally, various kinds of study have been performed so as to provide not only the absorbent characteristics but also the additional function to the water-absorbent resin by adding a deodorant and antibacterial compound to the water-absorbent resin.
Then, combinations of various kinds of deodorants and antibacterial agents have been proposed so as to provide the deodorant characteristic to the water-absorbent resin. For example, Patent Document 1 (Japanese Unexamined Patent Publication No. 158861/1985 (Tokukaisho 60-158861) (Publication date: Aug. 20, 1985)) recites a water-absorbent resin composition (absorbent agent) constituted of a water-absorbent resin and a theaceous plant leaf extract. Patent Document 2 (Japanese Unexamined Patent Publication No. 241030/1999 (Tokukaihei 11-241030) (Publication date: Sep. 7, 1999)) recites a water-absorbent resin constituted of a coniferous tree extract and a water-absorbent resin having a specific performance. Patent Document 3 (Japanese Unexamined Patent Publication No. 176338/1996 (Tokukaihei 8-176338) (Publication date: Jul. 9, 1996)) recites a deodorant water-absorbent resin composition in which zeolite particles are dispersed inside a water-absorbent resin compound. Patent Document 4 (Japanese Unexamined Patent Publication No. 51399/2000 (Tokukai 2000-51399) (Publication date: Feb. 22, 2000)) recites a persistent antibacterial deodorant constituted of (a) at least one kind of powder selected from a Japanese horse-radish extract, a mustard extract, and allyl isothiocyanate and (b) a water-absorbent gelatinizer for sustaining the antibacterial deodorant action of the powder. Patent Document 5 (Japanese Unexamined Patent Publication No. 79159/2000 (Tokukai 2000-79159) (Publication date: Mar. 21, 2000)) recites a powdery deodorant/antibacterial water-absorbent resin compound constituted of (a) a water-absorbent resin, (b) a compound having an antibacterial function with respect to an ammonifying bacteria, and (c) a medical agent having neutralizing ability with respect to ammonia, or having neutralizing ability and absorbing ability with respect to ammonia. Patent Document 6 (Japanese Unexamined Patent Publication No. 234087/2001 (Tokukai 2001-234087) Publication date: Aug. 28, 2001)) recites a water-absorbent resin composition in which a specific water-absorbent resin contains a water-soluble deodorant.
Further, techniques for providing the deodorant characteristic to an absorbing product using a water-absorbent resin are known. Patent Document 7 (Japanese Unexamined Patent Publication No. 41155/1990 (Tokukaihei 2-41155) (Publication date: Feb. 9, 1990)) recites an absorbing product containing manufactured tea and a water-absorbent resin. Patent Document 8 (Japanese Unexamined Patent Publication No. 135501/1988 (Tokukaisho 63-135501) (Publication date: Jun. 7, 1988)) recites a disposable diaper in which a water-absorbent resin contains benzalkonium chloride and/or chlorhexidine gluconate.
Further, as other techniques for providing the additional function by adding a deodorant and an antibacterial compound to the water-absorbent resin, techniques recited in the following documents are known. Patent Document 9 (Japanese Unexamined Patent Publication No. 139104/1992 (Tokukaihei 4-139104) (Publication date: May 13, 1992)) recites gelatinous insecticide obtained by making a water-absorbent resin absorb aqueous emulsion made mainly of volatile monoterpene compound. Patent Document 10 (Japanese Unexamined Patent Publication No. 59075/1991 (Tokukaihei 3-59075) (Publication date: Mar. 14, 1991)) recites a method for producing an antibacterial resin compound formed as follows: liquid made by dissolving antibacterial agent in volatile solvent is made to adhere to a water-absorbent resin, and the volatile solvent is removed thereafter, so that an antibacterial coating is formed on a surface of the water-absorbent resin. Patent Document 11 (Japanese Unexamined Patent Publication No. 179053/1993 (Tokukaihei 5-179053) (Publication date: Jul. 20, 1993)) and Patent Document 12 (Japanese Unexamined Patent Publication No. 165981/1995 (Tokukaihei 7-165981) (Publication date: Jun. 27, 1995)) recite a water-absorbent resin containing antibacterial phosphate. Patent Document 13 (Japanese Unexamined Patent Publication No. 116829/1999 (Tokukaihei 11-116829) (Publication date: Apr. 27, 1999)) recites a water-absorbent resin composition made of water-absorbent resin, tannic acid (salt), and complex silicate compound. Patent Document 14 (Japanese Unexamined Patent Publication No. 208787/1997 (Tokukaihei 9-208787) (Publication date: Aug. 12, 1997)) recites a water-absorbent resin composition obtained by internally providing or applying a natural antibacterial element, extracted from a grapefruit seed and/or a herb, to a water-absorbent resin. Patent Document 15 (Japanese Unexamined Patent Publication No. 285021/2002 (Tokukai 2002-285021) (Publication date: Oct. 3, 2002)) recites a particulate water-absorbent resin composition, including a plant powder and a water-absorbent resin whose surface has been treated, which has a deodorant index of not less than 180. Patent Document 16 (international publication pamphlet No. WO99/64485 (Publication date: Dec. 16, 1999)) recites a water-absorbent resin compound obtained by combining cyclodextrin and/or a cyclodextrin derivative to a water-absorbent resin by covalent bond and/or ionic bond. Patent Document 17 (international publication pamphlet No. WO01/41819 (Publication date: Jun. 14, 2001)) recites a water-absorbent resin composition made of water-absorbent resin and silver salt or colloidal silver.
However, although a general deodorant exhibits deodorant effect to some extent by chemically reacting with or absorbing odor elements, a deodorant effect with respect to odor of urine is hardly confirmed. Further, the deodorant cannot prevent microbes or bacteria from decomposing or putrefying organic matters. While, although a general antibacterial agent can prevent odor caused by decomposition or putrefaction, a deodorant effect with respect to odor of urine right after excretion is hardly confirmed. Further, it is general that merely adding a general deodorant compound to the water-absorbent resin may not sufficiently provide a deodorant performance to a whole absorbing product such as a paper diaper when such water-absorbent resin is used in the absorbing product.
Thus, the above-mentioned conventional methods for improving the deodorant characteristic sometimes does not exhibit sufficient effects in practical use, so that the absorbing product using the water-absorbent resin obtained by the conventional methods does not exhibit sufficient effects.
Further, high safety is so desired upon providing the deodorant performance so as to use the water-absorbent resin in an absorbing product and the like.